"Then what does it do?" said the lad, gazing hard in the direction of the north-west, where there was still a warm glow.

"Keeps up above the horizon."

"But that's what puzzles me," said Steve.

"Well, I hardly know how to explain it to you, my boy, unless you can grasp it if I ask you to suppose you are standing on the North Pole."

"Yes, I understand that. Wouldn't the sun set there?"

"No; but at midsummer day it would be at a certain height above the horizon."

"Yes; but how would it be at midsummer night?"

"Just at the same height in the sky, going apparently round the heavens."

"And would it keep on like that, always at the same height night and day?"

"Yes, for one day only. The next day it would be nearly the same height, then a little lower; and so it would go on becoming a little and a little lower, and, as it were, screwing slowly down till it was close to the horizon; then would come the days w